calvert



July 12, 1955 CALVERT 2,712,919

TORQUE AND TENSION CONTROL APPARATUS Filed July 14 1951 2 Sheets-Sheet l INVENTOR.

% wi %mw y 12, 1955 B. s. CALVERT TORQUE AND TENSION CONTROL APPARATUS Filed July 14,

2 Sheets-Sheet 2 INVENTOR.

prroex/a-v 2,712,919 Patented July 12, 1955 2,712,919 TQRQUE AND TENSIGN CONTROL APPARATUS Bert S. Calvert, Los Angel-es, Calif. Application duly 14, 1951, Serial No. 236,776 7 Claims. (Cl. 254-173) This invention relates to apparatus the movement of which is resisted by a force the intensity of which changes as the movement of the apparatus progresses. For example, such resistance is afforded by a spring, or other source of resistant energy which increasingly resists movement of the apparatus from its start.

A general object of the invention is to provide ap paratus, the operation of which develops a changing resistant force, said apparatus having features of construction that will alter the effect, and compensate for the change in intensity of the force. Probably the simplest example of such a changing resistance is that presented by a reel having a spring that resists the extension of a line or hose, the spring being mounted in such a way that as the line or a hose, becomes more and more extended the spring also becomes more extended and therefore exerts an increased resistant force.

As applied to such an environment an object of the invention is to construct the apparatus in such a Way that the torque exerted by the extended spring upon the apparatus can be maintained substantially constant in spite of the fact that the force actually exerted by the extended spring upon the apparatus is considerably greater than that exerted by the less extended spring when the apparatus commenced to operate.

in the present application the invention is described as applied to apparatus associated with a reel such as could be used to carry a tag-line attached to an excavator bucket.

But the utility of my invention is not confined to association with a tag-line, as it obviously can be employed associated with a hose reel from which a hose is drawn off. in that case it exerts its effect upon the reel to rewind the hose upon it. As herein used, the term flexible line is to be regarded as inclusive of cables, hoses, and the like.

In operating an excavator employing a bucket, particularly a bucket of the clam-shell type, suspended on a line, difhculty is experienced due to the fact that the bucket can twist about the axis of its supporting cable.

This diiiiculty is met by employing a line, popularly known as a tag-line, that runs off from a reel on the excavator and with its end attached to the bucket in such a way as to prevent the bucket from twisting or orienting itself away from the position in which it should face. It is common practice to employ a spring associated with the tag-line reel; but as generally employed, the tension in the line increases directly with the degree of extension of the tag-line. And in use there is considerable variation due to the fact that in its excavating movements the bucket considerably changes its distance from the tag-line reel. During all these changes the reel should promptly take up the slack in the line, and also must pay out the line freely under tension as may be necessitated by the buckets movements, and must not exert so much tension as to pull the suspended bucket to one side. When my improvement is applied to a tag-line, the tension can be maintained substantially constant, or nearly so, regardless of the degree to which the tag-line has been extended.

The present application is a continuation in part of my prior application Serial No. 163,067, filed May 19, 1950, now abandoned, and Serial No. 183,249, filed September 5, 1950, now abandoned.

In the preferred embodiment of the invention, it includes a differential device that enables a cable loop to be maintained under tension in such a way that it develops a substantially constant tension in the tag-line.

A spring is employed for maintaining the tension in the cable loop, and the differential device compensates for the changes in the force developed by the spring as it becomes more or less extended.

An object of the present invention is to provide an organization of elements for imparting force developed by a spring, which elements include differential means for developing opposing torques, and operating in such a way that when the spring is more extended and exerting a greater force, its power-arm is less, as it were, and when the spring is less extended its power-arm is greater. in this way the effective force imparted to the line is substantially uniform in all degrees of extension of the spring.

in the earlier filed application the apparatus included a torque member in the form of a drum having portions f different diameters, and employing what I call the cone-principle in controlling the relative value of the torques, the differential of which was employed to determine the degree of tension in the line. I

in my later filed application of the two referred to above, I employed a single tapered drum or cone along which runs from a tension-loop traveled as the line was pulled off the reel; the difference in diameter at the two points Where the runs led onto the cone determines the resultant torque force to resist pulling the line from the reel.

The present invention is an improvement that involves a new principle and feature involving a deviation of the drum from a straight side. The use of this principle enables the relation of the two opposed torques to be nicely controlled to compensate for greater force exerted by a greatly extended spring, or the weaker force exerted by a less extended spring. And in operation the appa:

. ratus compensates for the fact that a given amount of extension occurring after the spring has already been extended, causes a relatively greater increase in the force of the spring than if that same amount of extension occurs when the spring is less extended.

Further objects of the invention will be evident from a reading of the following specification and a study of the accompanying drawings.

In the drawings:

Figure l is a side elevation illustrating an excavator showing a tag-line connected to the same, and my control apparatus mounted near the base of the boom.

Figure 2 is a plan illustrating my tension control ap paratus which employs a duplex type of drum, in which my present improvement is employed.

Figure 3 is a plan of my control apparatus, of the single drum type, and this view also illustrates the application of my present improvement as it affects the form of the drum.

Figure 4 is a vertical section taken about on the line 4 4 of Figure 3.

Figure 5 is a plan upon a larger scale than Figure 3 showing the cone of Figure 3 removed from its supporting frame and shaft.

Figure 6 is a diagrammatic view illustrating how the torque forces developed by a cable loop co-operating with the cone, develop tension in the line that runs off the reel.

Figure 7 is also a diagrammatic view illustrating the way I prefer to construct the profile line of a cone such as shown in Figure to enable good effects to be attained in practicing the invention.

Figure 8 is a plan of an excavator bucket and illustrating how the end of the tag-line is attached to it to steady it and to dampen any tendency for it to oscillate on the cable fall that suspends it.

The invention consists in the novel parts and combination of parts to be described hereinafter, all of which contribute to produce an efficient torque and tension control apparatus.

A preferred embodiment of the invention is described in the following specification, while the broad scope of the invention is pointed out in the appended claims.

In Figures 1 and 2 an embodiment of the invention is illustrated, applied to a clam-shell type of excavator.

The type of excavator usually comprises a boom 1 pivotally supported on a horizontal pivot pin or shaft '2 on a turntable 3 that'is supported for rotation about a vertical axis on a tractor 4. The boom is supported in a more or less inclined position by means of a boom cable 5 attached as at 6 to the boom near its peak, and of course, this cable runs down over a sheave such as sheave 7, from which it passes into the cab 8 of the excavator where it is coiled on a drum (not illustrated).

The shell type bucket or clam-shell is suspended on the fall 9 of a bucket line 11 at the peak of the boom, and this line passes back over a sheave usually mounted co-axially with the sheave 7, and it passes into the cab and is coiled on its own drum.

The clam-shell 12 is composed of two sections 120 and 12b attached rigidly to two yokes 13 pivotally connected together on a hinge pivot 14, to which the shackle 14a is attached which hangs the bucket on the fall 9.

Within the cab 8, the operator of the excavator controls the line to let the bucket descend in an open position to the level where the earth or broken rock is being removed. Any of the usual means (not illustrated) is employed for holding the clam-shell open as it descends and for closing it to gather up its load.

When the .bucket has been raised to a suffici ently high level, the operator uses the ,control machinery in his cab '8 to swing the turntable about its vertical axis to bring the bucket over to the location where it is to be dumped. As this occurs, of course, the bucket tends to swing or whip out from the axis of the vertical" fall 9; and as the center of gravity of the load in the bucket'would rarely coincide with the center of gravity of the bucket itself, the bucket naturally tends to twist the fall 9 of the bucket line and orient itself, and to oscillate on the axis of the fall.

A tag-line'is employed to prevent this outward swing ing movement and the orientation and oscillation referred to above. a

In applying my invention to such an excavator, I provide a bail 15 that preferably includes two inclined links 15a and 15b that converge to a common connecting ring 16, their other 'ends being attached for free movement to eyes 17 near the ends of the bucket at its inboard side. to the ring 16, and its other My tag-line'18 is attached end is connected to mechanism (supported On the boom in this instance) for retracting the line and for maintaining the tension in the line as the tag-lineshortens, as it must when the bucket rises from its low-level digging position to a level suchas that indicated in Figure l, at which time the tag-line will be in a more or less horizontal position. V v

In order to accomplish this, I provide a differential Windlass 19, see Figure 2, which includes two drums 19a and 1911, the former-of which is of uniform diameter and the latter of whichis tapered and of slightly larger diameter than the drum 19a, These drums are mounted for rotation in unison and in the present instance'are attached rigidly to a shaft 20 that extends through 'them 10 that runs over a sheave instance the frame 32 clockwise direction as viewed in Figure 1.

- travelling'toward the small and is mounted for rotation near its ends in bearings at 21 and'22. Both of these drums are provided with helical grooves in which the ends of a cable 23 seat. The helical grooves are of opposite character and the cable ends are wrapped in opposite directions on these drums to ride the grooves. The end of the run of the cable 23a that passes around the drum 19b is anchored at 24 to a bolt or other suitable means. The end of the other run of the loop is similarly anchored on the outer end of the drum, but this connection is not illustrated. The end of the drum 19b, remote from the drum 19a, is of larger diameter than the end of this drum that lies adjacent to drum 19a.

Cable 23 is disposed in a loop 25 in which the sheave 26 floats, said sheave being carried in a block or shackle 27 the bight 28 of which is connected to a coil spring 29, which functions as means for'yieldingly maintaining tension in the cable 23 and the tag-line.

On the shaft 20 a reel 30 is mounted on which a portion of the tag-line 18 is disposed in coils 31. As illustrated in Figures 1 and 2, the tag-line 18 runs off from the reel 30 at its upper side. By reason of the tension in the two runs 23a and 23b of the cable 23, and by reason of the fact that even at its'small end the diameter of the drum 19b is greater than that of the drum 19a, it follows that the tension in these two runs of the cable 23 will bias the Windlass 19 for rotation in an anticourse, is because the cable run 23a has a greater lever arm or radius of action on the periphery of its drum than the run 23b has on its drum.

In Figure 2 the relation of the coils of cable on the drum corresponds to about the smallest extension of the spring 29. At this time the spring is exerting a relatively small force, so it needs a relatively high differential between the relative radii from the axis of the shaft to the point at which the cable run 23a is exerting its torque pull upon the drum.

In other words, when the line is pulled from the reel (with the parts as shown in Figure 2), the rotation of the reel will rotate the drum shaft 20 in a clockwise direction. This will shorten the loop 25'and extend the spring; but, as the spring is extended, the contact point of run 23:: with the perimeter of drum-portion 19b is diameter where the differential between the radii of the contact points of the cableruns is least. This, of course, operates to approximately equalize the efiective torque that resists the rotation of the reel; and is controlling the tension in the reel line. v

In order to attain an improved equalizing eifect, I prefer to give the large end of the drum portion 19b an outward flare having increased increments in diameter along the, length of the drum on its longitudinal profile line the effect of which is, that as the spring is returning to its state of least extension, the radius-differential will be increased at a greater rate than it would be when employing merely a straight-sided tapered cone.

In practice this Windlass would be preferably mounted in a frame 32 adapted in construction to rest upon a seat or bedplate on which it is to be mounted. In the present 7 would be adapted to seat on the upper side. of the boom land provided with side flanges 33 connected by a bridge bar 34 to provide a shaft bearing 22 at one end, and a frame structure 36 with a cross bar carrying a shaft bearing 21 at the other end.

Instead of employing a duplex or dual type of drum including a drum of uniform diameter, such as drum portion 19a, I may employ a single drum type of apparatus, such as illustrated in Figures 3 to 6 inclusive.

In this type-of apparatus I employ 'a single tapered drum 38, as the torque member, and I provide means for applying two torque forces to the drum surface at two points. removed .fromeach other by'one or two turns of a helical groove 39 that extends throughout the length of the drum as illustrated in Figure 3; the two runs 40 and 41 of the loop 42 run onto the drum at two traveling contact points 43 and 44 on opposite sides of the drum. The line 45 runs off from the upper side of the reel; hence as the drums 38 is rotated by the line 45, being pulled from the reel, the drum is rotated anticlockwise as viewed from the right end of the drum. This will unwind the coils 46 on the smaller end of the drum, and wind on more of the run 41. In other words the runs 40 and 41 travel toward the small end. And as the drum is flared toward its large end, as illustrated, the rate of flare is decreased continuously toward the small end where the differential between the radii R and 1' (see Fig. 6) is smaller than the differential when the contact points of the cable on the drum are nearer the large end of the drum. Of course, the smaller this differential is, the less will be the lever-arm or purchase for the spring. In other words, shortening the lever arm for the spring handicaps the spring and compensates against the increased force that the more extended spring exerts.

In the apparatus illustrated in Figures 3 and 4 I have illustrated two springs 48. These springs are anchored at one end to an angle bracket 49, the body of which is pivotally mounted to swivel on an adjustable threaded stem or long bolt 50, and the pull on the bracket by the two springs is resisted by an adjusting nut 51 on the thread of the stem 50. Although this adjusting stem 50 is illustrated as being rather short in Figure 3, it should be understood that in practice it would be long enough to enable any desired necessary adjustment, in the length of the spring, in order to determine the force that the spring will exert at the floating cross-head 52 to which the forward ends of the springs are hooked. This cross-head is part of a sheave block that carries the sheave 54 floating in the bight 55 of the loop.

In Figure 6 I illustrate diagrammatically the two torque forces by lines 40 and 41. These forces are applied to the torque member or drum 38 respectively at the points 43 and 44, the latter force being applied always at a slightly greater radius from the axis than the other force.

The periphery of the drum is provided with a guide for the coils that wrap on it, preferably in the form of a helical groove.

By having the sheave floating in the bight of the loop as illustrated in Figures 2 and 3, I avoid the use of a number of parts, and by using the swiveled supporting bracket and hooked ends for the springs, they and the sheave can maintain a straight line toward the contact points 43 and 44 during their travel along the drum.

in Figure 7 I illustrate the preferred form of the flare for the periphery of the drum 38. The angle formed between the longitudinal profile line of the flare and the axis increases from about 28 degrees at the small end of the drum, to about 50 degrees at the large end.

The longitudinal profile of the periphery of drum portion 56a is preferably disposed on a curve having the characteristics of the curve illustrated in Figure 7 so that the effective torque moment is delivered at a reducing rate of decreasing differential radius as the reel line or hose approaches the limit of its extension.

The amount of the biasing spring force that maintains the tension in the hose or tag-line, of course, will depend upon the size and force that the spring employed can exert. Of course, as any movement occurs in the bucket that lengthens or shortens the length of the loop, that is, changes its distance from the Windlass, it will lengthen or shorten the spring. Hence, this spring should not be too short but should have a sufiicient length, so that the changes that occur in its holding-effect on the sheave will not vary too greatly.

Other embodiments of this invention may be resorted to without departing from the spirit of the invention.

I claim as my invention, and ters Patent:

1. In a control apparatus for controlling tension in a line, the combination of a rotary part, the rotation whereof pays out the line or retracts the same, a differential device mounted to rotate in unison with the rotary member, a cable disposed in a loop with its runs connected to the differential device at different radii respectively, a sheave riding in the loop, traction means including an extensible spring for applying force to the sheave to maintain the runs of the loop in tension, said differential device having means for decreasing the differential between said radii as the spring becomes more extended, thereby controlling the action of the runs of said loop upon the same for maintaining substantially constant tension in the said line.

2. Apparatus for controlling tension in a flexible line, comprising a reel adapted to carry the line and being reversely rotatable to pay out and retract the line, a drum connected to said reel for rotation therewith and having a surface portion tapered axially of the drum, a cable disposed in a loop with its runs applied oppositely about the drum and extending therefrom at different drum radii by reason of a first of the runs being positioned on said tapered surface at a drum diameter greater than the diameter at the second run, a sheave riding in the lo p, and a spring connected to said sheave and applying tension to the runs of the loop, said spring being deformable at increasing resistance within itself to yieldably resist rotation of said drum and the reel as said line is payed out and acting to restore from its deformation to rewind the line on the reel, said first loop run traveling said tapered surface of the drum in a decreasing diameter direction but at diameters greater than the second run as the reel rotates to pay out the line, and the loop runs in relation to the drum hereby compensating for increasing resistance of the spring deformation.

3. Apparatus as defined by claim 2, in which said spring is a coil spring connected at one end to said sheave, and means for anchoring the opposite end of the spring.

4. Apparatus as defined by claim 2, in which said reel and drum are mounted for rotation about a common axis.

5. Apparatus as defined by claim 2, in which said tapered drum surface is concave axially of the drum.

6. Apparatus as defined by claim 2, in which both of said loop runs are wound on said tapered surface of the drum.

7. Apparatus as defined by claim 2, in which said tapered drum surface curves concavely axially of the drum at progressively decreasing angularity as the diameter decreases, and in which both of said loop runs are wound on said tapered surface.

desire to secure by Let- References Cited in the file of this patent UNFTED STATES PATENTS 2,939 Custer Feb. 4, 1843 20,888 Murna July 13, 1858 413,389 Cruikshank Got. 22, 1889 2,166,479 Ruddock July 18, 1939 2,189,447 Martin Feb. 6, 1940 2,454,365 Wollery Nov. 23, 1948 2,495,392 Smith Ian. 24, 1950 FOREIGN PATENTS 772,658 France Aug. 18, 1934 OTHER REFERENCES Watch and Clockrnakers Handbook, Dictionary and Guide, Britten, pp. 167, 168. 

